The present invention relates to a lithium-ion energy store and a method for matching potentials of a measurement section and of a main section of the lithium-ion energy store.
Lithium-ion energy stores have a high cell voltage and a good ratio between stored energy and weight and are therefore suitable for mobile applications, in particular for electrically operated vehicles. Lithium-ion energy stores are frequently manufactured as a wound construction, wherein a flat material is wound, which comprises two flat electrodes as well as a separator that electrically isolates the electrodes from one another. The electrodes typically comprise a metal collector which is preferably coated with an electrode material on both sides. Aluminum foil is typically used in the cathode electrode and copper foil in the anode electrode as the metal collector. The separator is usually imbued with an ion transport means which facilitates the passage of ions through the separator.
Lithium-ion energy stores are known as batteries and accumulators. It is furthermore known how to measure the current provided by a lithium-ion energy store with a multiplicity of different sensors, for example sensors comprising a shunt resistance or Hall sensors. Besides measuring means for the direct current flow, a multiplicity of other sensors and/or theoretical models, with which properties of lithium-ion energy stores can be acquired, exists. To this end, a number of specified properties of the energy store are typically acquired using the sensors and the theoretical models are applied to the acquired values in order to make inferences about the electrical properties or, respectively, the state of the energy store.
The European patent publication EP 2442400 A1 discloses an electrochemical cell which is based on lithium technology and comprises an internal reference electrode. Said reference electrode is embedded in the separator; thus enabling a reference cell to form between the reference electrode and each of the conventional electrodes of the cell. By specifying the properties of the two reference cells which represent the half cells of the energy store, information can be obtained about each of these half cells and therefore also about the entire energy store. In so doing, either the current of the entire cell is measured or a state of the energy store is inferred from other parameters or theoretical models. The additional electrode embedded in the separator prevents the ion flow at this location and carries the risk of a short circuit of the electrodes.